GENERAL BACTERIOLOGY 



93 



cotton filter at /. The whole apparatus is then steril- 

 ized in the autoclave at 120 C. for 5 minutes, and 

 connection is made through the flask (g) and the tube 

 (h) with the aspirator. Now aspirate some air through 

 the flask, disconnect at /, and set aside. Observe the 



FIG. 30 

 Action of Cotton Filter 



a Erlenmeyer flask 



b. Rubber stopper 



c. Glass tube 



d. Cotton filter 



e. Broth 



/. Bent glass tube with cotton filter at/ 

 g. Erlenmeyer flask 

 h. Tube connecting with aspirator 



results. Remove the cotton filter (d), and drop it 

 into a flask containing sterile broth; place in the 

 thermostat for 18-24 hours; examine and note the 

 conditions then present. 



Results of the exercises in this chapter are to be 

 observed by noting the appearance of colonies or 



